KR100623467B1 - Reduced noise electric motor for disk drive data storage devices - Google Patents

Abstract

The present invention provides an electric motor, preferably a disk drive spindle motor, comprising a multiphase stator driven by switching the phase of the drive current at the corresponding commutation angles of the rotor. By applying a semi-random small offset to the commutation angle where the drive current is switched, the excitation frequency is spread out over a wider range, reducing the peak harmonic excitation at the switching frequency. Preferably an offset table is retained, and offsets from that table are added to each rectifier point. The table preferably has more entries than the number of rectifiers, which are cycled in a round-robin fashion or otherwise.

Description

REDUCED NOISE ELECTRIC MOTOR FOR DISK DRIVE DATA STORAGE DEVICES

The present invention relates to an electric motor, and more particularly to a brushless DC spindle motor used to rotate a disk inside a disk drive data storage device.

In the second half of the 20th century, the information revolution came into being. While the information revolution is a broader development in history than any event or machine, no single device represents that information revolution than a digital electronic computer. The development of computer systems was clearly a revolution. Every year, computer systems are faster, store more data, and provide more applications to their users.

In modern computer systems, massive data storage needs demand large data storage devices. Various data storage technologies are available, but to date a rotating magnetic rigid disk drive is the most common. These disk drive data storage devices are very complex machines, with precise mechanical components, ultra-smooth disk surfaces, high-density self-encoded data, and complex electronics for controlling the encoding / decoding and driving behavior of the data. It contains a circuit. Thus, each disk drive is a unique miniature world that contains multiple systems and subsystems, each of which is required for proper drive operation. Rotating magnetic disk drives have a proven record of capacity, performance and cost despite this complexity, making them the best storage device for a wide range of applications.

Disk drives generally include one or more disks attached to a common hub or spindle, which are rotated at a constant speed by an electric motor, often called a spindle motor. Electric spindle motors are generally brushless DC-type motors, in which the motor comprises a multiple phase stator and a permanent magnet rotor, the different phases of the stator being sequentially excited by an electronic control device. This means that torque is applied to the rotor. Sequential switching and driving of different stator phases can cause mechanical vibrations at harmonic frequencies of the motor drive frequency of the disc. Such vibration is sometimes perceived as a high pitched sound by the user.

The humming noise generated by the disk drive storage device may be very annoying or confusing to the user, reducing the user's productivity. In addition, continued excitation at a particular frequency can have other undesirable side effects, such as possible interruption of servoing and deterioration of mechanical components.

Disk drive designers have long recognized that it is desirable to eliminate any spurious noise or vibration in the drive. Therefore, attention is paid to precision machining of mechanical parts and other methods and processes for noise suppression. However, noise reduction is not perfect, and there is still a need to find improved methods for reducing noise in disk drives, especially at harmonic frequencies of disk motor drive frequencies.

According to the invention, the electric motor, preferably the spindle motor of the disc drive, comprises a multiphase stator driven by switching the phase of the drive current at a corresponding commutation angle of rotation of the rotor. . The commutation angle at which the drive current is switched is subject to small variations, referred to herein as a semi-random offset. These fluctuations have the effect of spreading the frequency of excitation over a wider range, thus reducing the peak harmonic excitation at the switching frequency.

In a preferred embodiment, a table of small, semi-random phase shift offsets is maintained, the offset from which the phase changes occur at the commutation point (i.e. drive current). Point or angle). In one variation of this embodiment, offset entries are retrieved from the table in round robin order and added to the rectifier point. The number N of entries in the table is preferably more than the number P of commutation points in one revolution of the rotor and is a prime number or a number that does not have a common factor with P. Thus, the semi-random pattern of phase shift is repeated every N disk revolutions. If necessary, N can be made large enough so that the fundamental frequency of pattern repetition from the table is so low that it is not perceived.

Preferably, a semi-random commutation offset is not used during the spin-up period in which the electric drive circuit is trying to raise the motor to its rated operating speed, and the motor operates. Only used after the speed has already been reached. This avoids unnecessary interference with the spin-up process of the disk assembly.

Thus, an electric motor constructed in accordance with the present invention is expected to generate less noise perceived by the user and also have additional additional benefits due to the reduction of mechanical vibrations at the switching harmonic frequencies of the motor.

DETAILED DESCRIPTION Details of both the structure and operation of the present invention will be understood with reference to the accompanying drawings, in which like parts are provided with the same reference numerals.

1 is a simplified diagram of a rotating magnetic disk drive storage device for use in accordance with a preferred embodiment of the present invention.

2 is a high level diagram of the major electronic components of a disk drive storage device, according to a preferred embodiment.

3 is a partial cross-sectional view of a disk drive spindle motor in the plane of the axis of rotation, according to a preferred embodiment.

4 is a simplified cross-sectional view of a disk drive spindle motor in a plane perpendicular to the axis of rotation, according to a preferred embodiment.

5 is a high level flow chart of a process for operating a disk drive spindle motor, according to a preferred embodiment.

Disk Drive Design Overview

Rotating magnetic rigid disk drives generally include one or more smooth, flat disks permanently attached to a common spindle or hub. If more than one disk is used, these disks are stacked on the spindle at intervals from each other, parallel and non-contact with each other. The disk and the spindle are all rotated at a constant speed by the spindle motor.

Spindle motors are generally brushless DC motors with multiphase electromagnetic stators and permanent magnet rotors. Different phases of the stator are driven sequentially by the drive current to rotate the rotor.

Each disk is formed of a solid disk-shaped base or substrate, with a hole for the spindle at its center. The substrate is usually aluminum, but glass, ceramic, plastic or other materials are possible. The substrate is coated with a thin layer of magnetic material and may additionally be coated with a protective layer.                 

Data is recorded in the magnetization layer on the disk or the surfaces of the disks. For this purpose, a micromagnetization pattern representing data is formed in the magnetization layer. Data patterns are usually arranged in circular concentric tracks, but spiral tracks are also possible. Each track is also divided into a number of sectors. Therefore, each sector forms an arc, and all sectors of the track form a circle.

To read or write data, a moveable actuator positions the transducer head near the data on the surface. The actuator may be likened to the tone arm of a gramophone, and the head to analogy to a regeneration needle. There is one transducer head for each disk surface that contains data. Actuators usually position the head by rotational movement about an axis parallel to the axis of rotation of the disk (s). Actuators are generally solid blocks with comb-like arms (sometimes referred to as "combs") that surround the axis and extend towards the disc, as long as they are attached to the arm. It includes a thin suspension of the set and an electromagnetic motor on the opposite side of the shaft. The transducer head is attached to the end opposite the comb of the suspension, with one head for each suspension. The actuator motor rotates the actuator to position the head above the desired data track (seek operation). Once the head is located on top of the track, the constant rotation of the disc eventually causes the desired sector to be adjacent to the head, and then the data can be read or written. Actuator motors are generally electromagnetic coils mounted on an actuator comb and a set of permanent magnets mounted at fixed positions on a base or cover, which, when powered, responds to the magnetic field generated by the permanent magnets. Torque the comb.

In general, a servo feedback system is used to position the actuator. The servo pattern for identifying the data track is recorded on at least one disk surface. The transducer periodically reads this servo pattern to determine the current deviation from the desired radial position, and the feedback system adjusts the position of the actuator to minimize the deviation. Previous disk drive designs often used dedicated disk surfaces for servo patterns. Newer designs generally use an embedded servo pattern. That is, the servo pattern is recorded in portions at angular intervals on each disk surface, and the area between the servo patterns is used to record data. The servo pattern generally includes a synchronizer, a track identifier that identifies the track number, and a track centering portion for locating the centerline of the track.

The transducer head is a block of material (usually ceramic) with an aerodynamic shape, on which a magnetic read / write transducer is mounted. This block or slider floats a very small distance on the surface of the disk (called “flyheight”) as the disk rotates. Proximity to the disk surface is important for enabling the transducer to read or write the pattern of data in the magnetization layer. Several different transducer designs are used. Many current disk drive designs use thin-film inductive write transducer elements and separate magneto-resistive read transducer elements. The suspension actually forces the transducer head towards the disk surface. The aerodynamic properties of the slider counter this force, allowing the slider to float on the disk surface at a suitable distance for data access.

Referring to the drawings, wherein like numerals represent like elements throughout the several views, FIG. 1 is a schematic diagram of a rotating magnetic disk drive storage device 100 for use in accordance with the preferred embodiment. Disk drive 100 includes a rotating disk 101, which is rigidly attached to a hub assembly or spindle 103 mounted on a disk drive base or housing 104. have. The spindle 103 and the disk 101 are driven at a constant rotational speed by a drive motor. A drive motor (not shown in FIG. 1) is included in hub assembly 103. Data is recorded on the top and bottom surfaces 102 of each disc. The actuator assembly 105 is located on one side of the disk 101. The actuator 105 is rotated in an arc around a shaft 106 parallel to the axis of the spindle driven by the electromagnetic motor 107 to position the transducer head. A cover (not shown) is mated with the base 104 to enclose and protect the disk and actuator assembly. Electronic circuit modules for controlling the operation of the drive and communicating with other devices, such as host computers, are mounted on a circuit card 112. In this embodiment, the circuit card 112 is shown mounted outside the enclosure formed by the base 104 and the cover. However, the card 112 may also be mounted inside the head / disk enclosure, or some of its electronic circuitry may be mounted inside the case and others may be mounted outside the enclosure. The plurality of head / suspension assemblies 108 are secured to the prongs of the actuator 105. An aerodynamic slider 109 with read / write transducer 110 is adjacent the disk surface 102 at the end of each head / suspension assembly 108.

Although disk drive 100 is shown as having two disks having a plurality of recording disk surfaces, the present invention records data that can utilize a drive having only one disk or a larger number of disks. It will be appreciated that it is possible to use only one disk surface of the disk to do this.

Figure 2 is a schematic diagram of the main electronic components of the disk drive 100, showing how they are connected to each other and to the transducer head, actuator motor and spindle motor in accordance with the preferred embodiment. File controller 201 provides a data interface to the host. "Host" generally refers to a computer system, such as a desktop computer system or a mainframe computer system, but for a special purpose such as a personal digital assistant (PDA), a digital controller of a machine such as a car or robot, or any other digital device. It may be a device. File controller 201 also provides overall control over the operation of disk drive 100, including functions such as command interpretation, sector mapping, power up routines, diagnostics, error recovery, and the like. Channel circuitry 202 provides the modulation and demodulation function of the data written to and read from the disk surface. The servo processor 203 interprets the servo signal obtained by reading the servo pattern on the disk to control the actuator and the spindle motor, and also responds to a seek signal from the file controller 201. The servo processor 203 determines the parameters required for the actuator motor and the spindle motor, and provides them as inputs to the actuator motor drive circuit portion 204 and the spindle motor drive circuit portion 205. Actuator motor drive circuitry 204 then provides a drive current to actuator voice coil motor (VCM) 107 to position actuator 105 to a desired location. The spindle motor drive circuitry 205 provides a drive current to the spindle motor 206 to drive the motor at a desired rotational speed, as described in more detail below.

The transducer 110 is connected to the write multiplexer 213 and the read multiplexer 211 via lead wires, which are then connected to the write driver 212 and the read amplifier 210, respectively. Read amplifier 210 provides an input to channel circuitry 202. The channel circuitry provides an input to the write driver 212. Multiplexers 211 and 213 select either one of the heads for writing or reading in response to control signal 214 from file controller 201. The magnetic pattern representing the data or servo signal is sensed by the magnetoresistive read element in the transducer 110, amplified by the read amplifier 210 and provided to the channel circuitry 202. The channel circuitry preferably includes a partial-response maximum likelihood (PRML) filter for decoding the data signal into coherent data for use in the host system. When writing data, the channel circuit section 202 encodes the data according to a predetermined encoding format and provides this data to the write driver 212, which then drives a current to drive the inductive recording element. (inductive write element) to allow data to be written on the disk surface.

Positioning of transducer 110 includes servo feedback including transducer 110, read amplifier 210, channel circuitry 202, servo processor 203, actuator driver 204, and actuator motor 107. Achieved by a loop system. The transducer 110 reads the servo patterns recorded on the disk surface 101 at periodic intervals, which are amplified by the read amplifier 210, and the servo patterns are converted into position information by the channel circuit section 202. Converted, the positional information is interpreted by the servo processor 203 to determine the amount of drive current to be supplied to the actuator motor 107, and the actuator driver 204 then responds to a control signal from the servo processor 203 To generate the required drive current. The servo processor 203 uses the same information to interpret the angular position and provide the appropriate control signal to the spindle motor driver 205.

File controller 201 preferably includes a programmable processor 221 that executes control program 231 residing in read-only memory (ROM) 222. ROM 222 is a nonvolatile semiconductor random access memory whose contents are not lost when the disk drive 100 is powered off. The ROM also includes a randomizing table 232, which contains a set of random angular offsets for commutation of the spindle motor 206, as described in more detail below. The file controller also includes volatile read / write memory (RAM) 223. RAM 223 is used as a temporary cache for data read from one or more disk surfaces and data to be written thereto. The RAM 223 is also used to store internal state variables required for the drive operation.

While some disk drive features have been shown and described above, particularly with respect to separately configured magneto-resistive read and inductive write transducer elements, these are merely illustrative of the preferred embodiment and may be described as other transducer elements or It will be appreciated that it is also possible to practice the invention using other alternative disk drive design features. Also, for purposes of explanation, FIG. 2 shows various electronic components, such as file controller 201, channel 202, and servo processor 203, one or more of which may be integrated as a single module or implemented in multiple modules. It will also be understood.

In a preferred embodiment, the spindle motor 206 is a brushless DC motor of a so-called "in hub" design, with a multiphase electromagnetic stator and a permanent magnet rotor. 3 is a partial cross-sectional view of the spindle motor 206 in the plane of the axis of rotation. The motor 206 includes a base 301, which is fixed to the base 104 of the disc drive 100. The rotor housing 302 surrounds various motor components. The rotor housing includes a central shaft portion 310, which is engaged with a bearing 303 mounted on the hollow cylindrical protrusion 312 of the base 301.

The rotor housing includes a flange 311 protruding from the outer bottom edge in proximity to the base. One or more discs 101, when installed in the disc drive 100, are inserted into the rotor housing 302 and supported by flanges 311, which then rotate the center opening of the disc 101. Protruding through, the disks are clamped to the flange with clamps and spacers (not shown). The disk is thus clamped to rotate integrally with the rotor housing 302.

A multi-pole stator 305 comprising a plurality of sets of iron laminations 306 surrounded by each winding coil 307 is secured to a cylindrical protrusion 312 of the base 301. Alternately spaced permanent magnets of alternating polarity (circumferentially polarized magnets) at fixed intervals along a plurality of circumferential directions are fixed to the rotor housing 302 to move the moving field generated by the stator 305. Torque is applied to the rotor housing 302 in the presence of an electro-magnetic field.

4 is a simplified cross-sectional view of the motor 206 in a plane perpendicular to the axis of rotation. 4 shows the arrangement of a plurality of stator poles and rotor magnets, the stator windings being schematically shown for simplicity of explanation. The stator windings are arranged in three phases as shown, with three poles in each phase, for a total of nine poles 401-409. All windings of one phase are in series. The three phases are connected to each other by a known "Y" connection, where all phases are connected to a common central node. In operation, current is always driven through two phases by driving through the first phase in the forward direction and through the second phase in the reverse direction. For example, if the current source driver on phase A is switched on and the current sink driver on phase B is on, the current is wound in series from the A phase line. Pass 401, 404 and 407, and back out in series through the B phase windings 408, 405 and 402 through the B phase line. In this case, the reason why no current flows in the C-phase winding is that both the C-phase driver and the sink are switched off. The driving magnetic field of the stator is rotated by changing a pair of driven phases. The permanent magnets 421-432 are arranged in alternating polarity along the circumferential direction on the inner cylindrical surface of the rotor housing 302 as shown. This magnet "chases" the rotating drive magnetic field, causing the rotor to rotate at the rotational speed of the drive magnetic field.

In the typical stator / rotor pole arrangement of FIG. 4, each of the pair of driving phases of the stator of the stator is reversed per pole of revolution of the rotor. That is, the phase pair is A-B, A-C, B-C for one pole and B-A, C-A, C-B for the next pole. This means that in the case of a three-phase stator and a twelve-pole rotor, the pair of stator phases of the stator must change 36 times in order to drive the rotor and make one full revolution. Thus, in this arrangement, whenever the rotor rotates every 10 degrees, there must be a change in the pair of phases of the stator being driven. The angular position of the rotor in which the stator phase is switched is called the commutation point. In conventional motors, the nominal commutation point is at 0 °, 10 °, 20 °, 30 °, etc., from any angular reference position of the rotor. According to the present invention, a minor random-like variation is applied to these rectification points. For example, in any particular rotation, commutation can occur at 0.23 °, 9.89 °, 19.97 °, 30.30 °, ... It is desirable to ensure that commutation does not occur at the same set of points in each revolution, so that the commutation point is different at the next revolution of the rotor.

It will be appreciated that many variations are possible in the arrangement of the stator and rotor poles. In Fig. 4, the poles of 12 permanent magnets are attached to the rotor and the stator comprises 9 poles (three phases each having 3 poles), but those skilled in the art will appreciate the poles of the permanent magnets, the stator poles. It will be appreciated that the number of stator phases may vary, and so may the number of rectifier points. It will also be appreciated that the stator phases may be connected in a "delta configuration" or, as an additional variation, the "Y" connection described above may include a center tap capable of supplying any single phase. In addition, by providing a separate drive circuit and / or a separate drive line for the windings of the same phase, it may be possible to cause the windings to be driven in parallel rather than in series.

It will also be understood that FIGS. 3 and 4 are intended to schematically illustrate the major components of a typical disk drive spindle motor. Various modifications are possible in the design and arrangement of bearings, magnets, coils, clamping mechanisms and the like within the scope of the invention.

For commutation, the servo processor 203 must determine the current angular position of the rotor. In the preferred embodiment, the positional information read by the read transducer and decoded by the channel 202 is used to determine the angular position when the rotor is rotating at operating speed. In general, another alternative method is used during the power-on routine while the motor is going up from the standstill to operating speed. As another alternative, any of a number of other alternative methods may be used at the speed of operation. Another alternative is to sense a back EMF of the stator coil or to provide a separate sensor mechanism, such as a magnetic encoding wheel. The servo processor 203 uses the positional information to determine not only the magnitude of the required drive current, but also the stator phase pairs to be driven, input these parameters to the spindle motor driver 205 and then the spindle motor. Driver 205 generates the required current.

Preferably, the servo processor 203 includes a commutation register 225 that stores the commutation point and the corresponding motor phase to drive. The servo processor 203 compares the current rotor position with the values in the rectification register 225 to determine the exact pair of phases of the stator to drive. The commutation register 225 preferably has 36 entries sufficient for one full revolution of the rotor, but may have fewer entries circulated in a round-robin fashion.

In a preferred embodiment, the control program 231 executed in the processor 221 of the file controller 201 controls the operation of the disk drive 100 to change the values in the rectifying register 225 and thus the servo processor. Let 203 cause a small, semi-random variation at the rectifier point. This process is shown schematically in FIG.

As shown in FIG. 5, the disk drive 100 is initially in an off state. In the "off" state, no power is applied to the spindle motor. The disk drive 100 exits the off state upon the occurrence of a power up event (block 501). This can be done in any of several ways. The disk drive 100 may be completely powered off. That is, it may be truly “off”, in which case the disk drive 100 exits the off state when it is powered from an external source such as an ignition switch (exit block 501). Thus, power is supplied to the controller 201 and the control program starts execution in the processor 221. Alternatively, external power can always be applied to the drive, but controller 201 can shut off power to the spindle motor, channel and other electronic circuitry. In this alternative, processor 221 waits for some external command, interrupt or similar event in an idle loop and exits from block 501.

Exiting from block 501, the control program 231 starts powering up the disk drive, which includes raising the spindle motor 206 to operating speed (step 502). In general, the disc transducer cannot read the data recorded on the disc until the spindle motor is near its operating speed. Thus, the controller sends an appropriate power up command to the servo processor 203 to put the servo processor 203 in a power up state. At about the same time, the controller 201 transmits a set of values for storage in the commutation register 225, which values are nominal commutation points of the spindle motor 206 (ie, 0, 10, 20, 30... .)to be. In some cases, the motor may have difficulty starting, and the controller may cause movement by any of a variety of known starting techniques.

When the servo processor 203 is in the power-on state, the servo processor 203 causes the spindle motor driver 205 to drive each stator winding pair with a predetermined starting current (usually the maximum allowable value). The servo processor determines the angular position as described above and compares it with the nominal commutation value in register 225 to switch the stator phase pairs on reaching the respective commutation point.

The control program then checks the power up timer (step 503) while waiting for the motor to reach operating speed (step 504) as an alternative. It may take a few seconds for the motor to reach operating speed. During this period, the controller may be performing diagnostics or other functions, but the servo processor 203 continues to drive the spindle motor 206 at the rated starting current using the nominal commutation value stored in the register 225. If the motor does not reach the operating speed within the predetermined maximum period, the " yes " branch is followed in step 503, an error message is generated (step 505), and the drive is powered down (step 506). If the operating speed is reached before timeout, then follow step “504”.

After reaching the operating speed, the control program initializes the index variable of the randomization table 232 (step 510). The table 232 has an array of offset values to be added to the nominal commutation angle to determine the actual commutation value that the servo processor 203 will use to switch the stator phase. The values in the table 232 may be generated by any random or semi-random process, or calculated to be not random at all but only appear to be random or distributed when added to the nominal commutation angle as described herein. . These values are stored permanently in ROM 222, and therefore the values do not change. The number of values stored in the table 232 is preferably more than the number of commutation points in one revolution of the rotor, ie more than 36 in the configuration of the preferred embodiment. To increase the randomly visible nature of the offsets during operation, the number of entries in the table 232 is either a prime number or a composite number with no common factor and the number of commutation points in one revolution of the rotor. Is preferable.

The control program then generates a set of 36 commutation points (commutation angles) for every complete revolution of the rotor, as shown as steps 511 to 514. The control program first initializes the loop variable i to 1 (step 511). Then, one rectification point CP (i) is the sum of the nominal rectification point CP _N (i) corresponding to the loop variable and the offset from the table 232 corresponding to the table index variable. Is calculated. The control program then increments the loop variable i and the table index variable (step 513). The loop variable i is incremented by 1 and the table index can be incremented by 1 to simply cycle through the entries in the table 232 in a round-robin fashion, but in other alternatives additional variability can be achieved by incrementing the table index in some other way. It will also be possible to achieve variability. For example, the table index can be incremented by the current i value or by some lower order bits in the system clock. Since the number of table index values must not exceed the number of entries in the table 232, the new index is incremented with the previous index, i.e. modulo N (N is the number of entries in the table 232). ] Is added to.

The control program then checks the value of i (step 514), and if the value exceeds 36 (the number of commutation points in one revolution), steps 512 and 513 are repeated. If 36 new rectifiers have been generated in this way, follow the " yes "

The control program then waits for the spindle motor to complete the current rotation (step 515). When the rotation is complete, follow step “Yes” in step 515. The control program then sends the controller 201 to the 36 new rectifier point values, which are stored in the corresponding entry in the rectifier register 225 (step 516). This allows the new setpoint values to be used in subsequent rotations of the rotor.

If no power down indication has been received (step 517), the control program returns to step 511 to calculate a new set of setpoint values for the next rotation of the rotor. If a power down indication has been received, follow the " yes " branch in step 517 and the motor is powered off (step 506).                 

It will be appreciated that a disk drive operation that is not related to spindle motor operation is not shown in FIG. 5. In fact, the control program 231 generally includes a number of concurrently executing tasks, and the spindle motor control is just one of them. A typical disk drive responds to many different types of commands, the response behavior can be very complex, the exchange of information with the host can take many steps, and so on. These details are omitted herein for simplicity of explanation.

In general, the routines executed to implement the illustrated embodiments of the invention, whether implemented as part of an operating system or as a particular application, program, object, module or instruction sequence, are referred to herein as a "program". Or "control program". This program, when read and executed by one or more processors in computer systems or systems in accordance with the present invention, generally causes the devices or system to perform the steps or elements thereof for carrying out various aspects of the present invention. It contains instructions that allow you to perform the steps necessary to create elements. In addition, although the present invention has been described with reference to fully functioning digital devices such as disk drives and the like, as will be described later, various embodiments of the present invention may be distributed as various types of program products. The invention applies equally regardless of the particular type of signal-bearing media used to actually perform its distribution. Examples of signaling media include recordable type media, such as volatile and nonvolatile memory devices, floppy disks, hard-disk drives, CD-ROMs, DVDs, magnetic tapes, and digital and wireless communication links. Transmission-type media, such as analog communication links, include, but are not limited to. Examples of signaling media are shown in FIG. 1 as disk surface 102 and in FIG. 2 as ROM 222.

In the preferred embodiment described above, a brushless DC electric motor is used as the spindle motor of the rotary magnetic disk drive data storage device. However, these motors can also be used in other environments. This motor may alternatively be used as a spin motor for an optical disc data storage device such as a CD-ROM, DVD-ROM or audio CD player. This motor can also be used as a drive motor for a magnetic tape data storage device. Finally, such a motor can be used as an electric motor in any number of applications that are not related to data storage.

In a preferred embodiment, the control program running on the programmable processor of the disk file controller generates a rectification point with reference to a table of semi-random offsets and transfers this data to the commutation register used by the servo processor. To perform the actual rectification. This configuration not only provides significant design flexibility, but also provides the ability to disable the use of semi-random offsets during motor startup. However, it will be appreciated that semi-random small variations in the rectification point can be achieved using many different hardware and software variations. For example, the servo processor itself may cause a change in the commutation point or the servo processor may contain all the motor control logic.

In a preferred embodiment, a set of offset values is stored in a randomization table, which is added stepwise to the commutation angle, resulting in the effect of random small variations in the commutation angle. Such a table is preferred to facilitate the calculation. Those skilled in the art will appreciate that there are a number of ways to achieve a similar effect. For example, a random number calculation function or special apparatus can generate so-called random numbers for adding to the nominal commutation angle. It is also possible to derive an offset according to any complex pattern that is not entirely random but is only intended to spread the motor noise spectrum at harmonic peaks associated with the commutation frequency. As used herein and in the claims, “semi-random offset” is used for the purpose of encompassing any method of obtaining a dispersion of offsets from any nominal commutation profile. As the method described herein, as well as other methods include.

Claims (24)

A rotating magnetic disk drive data storage device comprising: Disk drive base, A rotatably mounted disk and spindle assembly having at least one rigid disk, the at least one rigid disk for recording magnetically encoded data on at least one surface thereof. Said disc and spindle assembly being permanently mounted to said disc and spindle assembly, A movable actuator for supporting at least one transducer head, said positioning said at least one transducer head on said at least one surface of said at least one rotatably mounted disk for accessing said self-encoded data; Phosphorus and the movable actuator, A spindle motor for rotating said at least one rotatably mounted disk and spindle assembly, said spindle motor having a multi-phase electro-magnetic stator and a permanent magnet rotor; , And A spindle motor drive, wherein the spindle motor drive provides drive current to the multiphase electromagnetic stator, the spindle motor drive sequentially steps phases of the drive current at corresponding rotation angles of the disc and spindle assembly. And the spindle motor drive device changes each successive rotational angle when the spindle drive motor drive device switches the phase of the drive current by a respective semi-random offset. Rotating magnetic disk drive data storage device comprising a. The rotating magnetic disk drive data storage device of claim 1, wherein each of the semi random offsets is obtained from a table including a plurality of semi random offset values. 3. The apparatus of claim 2, wherein the spindle motor drive uses sequential semi random offset values from the table in a round-robin pattern, wherein the number N of semi random offset entries in the table is the electromagnetic. A rotating magnetic disk drive data storage device having more than the number P of commutation points in the stator. 4. The rotary magnetic disk drive data storage device of claim 3, wherein the greatest common divisor of N and P is one. The spindle motor driving apparatus of claim 1, wherein the spindle motor driving device does not change each subsequent rotational angle by the respective semi-random offset when the spindle motor is turned on until the spindle motor reaches a predetermined rotational speed. And vary each subsequent rotation angle by the respective semi-random offset after it is reached. According to claim 1, The spindle motor drive device, Memory, A programmable processor executing a control program stored in said memory, and And a servo processor responsive to control parameters generated by the programmable processor. The apparatus of claim 6, wherein the servo processor includes a rectifying register for identifying a plurality of rectifying points, Data in the rectifying register is provided by the control program running on the programmable processor. In the electric motor for a disk drive, Base, A multiphase electromagnetic stator mounted on the base, A rotor rotatably mounted to the base, the rotor having at least one permanent magnet that rotates the rotor in response to an alternating magnetic field generated by the stator; and A motor drive device, wherein the motor drive device provides a drive current to the polyphase electromagnetic stator, the motor drive device sequentially switches phases of the drive current at corresponding rotation angles of the rotor, In addition, the motor drive device is to change each of the successive rotation angle when the motor drive device to switch the phase of the drive current by each semi-random offset, the electric drive for a disk drive comprising the motor drive device motor. The electric motor of claim 8, wherein each of the semi random offsets is obtained from a table including a plurality of semi random offset values. 10. The apparatus of claim 9, wherein the motor driving apparatus uses the sequential semi random offset values from the table in a round-robin manner, and the number N of semi random offset entries in the table is the number of rectifier points in the electromagnetic stator. An electric motor for a disk drive that is more than P. 12. The electric motor of claim 10, wherein the greatest common divisor of N and P is one. The motor driving apparatus of claim 8, wherein the motor driving device does not change each subsequent rotational angle by the respective semi-random offset when the electric motor is turned on until the electric motor reaches a predetermined rotational speed. And then change each next rotation angle by the respective semi-random offset. The method of claim 8, wherein the motor drive device, Memory, A programmable processor executing a control program stored in the memory, A commutation register for identifying a plurality of commutation points, wherein data in said commutation register is provided by said control program running on said programmable processor, and And a rectifier for switching the phase of the drive current at the rectifier points specified by the rectifier resistor. The electric motor of claim 8, wherein the motor is a spindle motor for rotating one or more data storage disks of a rotating magnetic disk drive data storage device. A method of operating an electric motor for a disk drive, the electric motor having a multiphase electromagnetic stator and a rotor, the rotor having at least one permanent magnet rotating the rotor in response to an alternating magnetic field generated by the stator. In the, the method for operating the electric motor for the disk drive, Defining a plurality of nominal commutation angles for switching corresponding phases of said electromagnetic stator driven by a current;  Adding a respective semi-random offset to each of its nominal rectification angles to yield a corresponding plurality of adjusted rectification angles, and Switching the phase of the electromagnetic stator driven by a current at the corresponding plurality of adjusted rectifying angles. 16. The method of claim 15, wherein adding each semi random offset to each respective nominal commutation angle comprises obtaining the respective semi random offset from a table comprising a plurality of semi random offset values. How to operate an electric motor for a disk drive. 17. The method of claim 16, wherein obtaining the respective semi random offset from a table comprises accessing a plurality of semi random offset values in the table in a round-robin fashion, wherein the semi random offset entry in the table is selected. The number N is greater than the number P of rectifier points in the electromagnetic stator. 18. The method of claim 17, wherein the greatest common divisor of N and P is one. 16. The method of claim 15, wherein adding each semi-random offset to each respective nominal commutation angle to calculate a corresponding plurality of adjusted commutation angles is performed until the electric motor reaches a predetermined rotational speed. A method of operating an electric motor for a disk drive, which is to be performed after it has been reached.  A computer-readable recording medium having recorded thereon a program for controlling the operation of an electric motor for a disc drive, the electric motor having a multiphase electromagnetic stator and a rotor, the rotor in response to an alternating magnetic field generated by the stator. A computer readable recording medium having recorded thereon a program for controlling the operation of an electric motor, the method comprising: at least one permanent magnet rotating a rotor; The program includes a plurality of processor-executable instructions recorded on a signaling medium readable by a controller of the electric motor, The instructions cause the motor controller to execute the following steps when executed by the processor, i.e. Defining a plurality of nominal commutation angles for switching corresponding phases of the electromagnetic stator driven by a current,  Adding a respective semi-random offset to each of its nominal rectification angles to yield a corresponding plurality of adjusted rectification angles, and A computer readable recording medium having recorded thereon a program for controlling the operation of an electric motor for a disk drive, the step of switching the phase of the electromagnetic stator driven by a current at the corresponding plurality of adjusted rectifying angles. . 21. The method of claim 20, wherein adding each semi random offset to each respective nominal commutation angle comprises obtaining the respective semi random offset from a table that includes a plurality of semi random offset values. And a computer readable recording medium having recorded thereon a program for controlling the operation of an electric motor for a disk drive. 22. The method of claim 21, wherein obtaining the respective semi random offset from a table comprises accessing a plurality of semi random offset values in the table in a round-robin manner, wherein The number N is greater than the number P of rectifier points in the electromagnetic stator, wherein the program for controlling the operation of the electric motor for the disc drive is recorded. 23. The computer readable recording medium as claimed in claim 22, wherein a maximum common divisor of N and P is 1. 21. The method of claim 20, wherein adding each semi-random offset to each respective nominal commutation angle to calculate a corresponding plurality of adjusted commutation angles is performed until the electric motor reaches a predetermined rotational speed. A computer readable recording medium having recorded thereon a program for controlling the operation of an electric motor for a disk drive, which is not performed but is performed after it is reached.

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